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| Open AccessTheory of low-power ultra-broadband terahertz sideband generation in bi-layer graphene
In terahertz sideband generation, an electron–hole pair is accelerated in a semiconductor by a terahertz field to then recombines forming a frequency comb, but so far experimental realizations have relied on the large fields of free electron lasers. Here, Crosse et al.propose bi-layer graphene for sideband generation at lower fields.
- J. A. Crosse
- , Xiaodong Xu
- & R. B. Liu
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Real-space observation of unbalanced charge distribution inside a perovskite-sensitized solar cell
The performance of perovskite solar cells has improved dramatically over just a few years but our understanding of how they work is incomplete. Bergmann et al.use Kelvin probe force microscopy to map the electric potential in these cells to show that an accumulation of holes could limit this performance.
- Victor W. Bergmann
- , Stefan A. L. Weber
- & Rüdiger Berger
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Germanium avalanche receiver for low power interconnects
Despite many recent advances in silicon photonics for optical telecommunications and on-chip optical interconnects, the issue of power consumption has not been fully addressed. Here, Virot et al. propose a waveguide avalanche germanium photodiode suitable for low power consumption interconnects.
- Léopold Virot
- , Paul Crozat
- & Laurent Vivien
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Nonlinear optics of fibre event horizons
Fibre optic event horizons have been described in the time domain where a soliton-induced refractive index barrier modifies the velocity of a probe. Here, Webb et al.describe horizon dynamics in the frequency domain in terms of cascaded four-wave mixing between discrete single-frequency fields.
- Karen E. Webb
- , Miro Erkintalo
- & Stuart G. Murdoch
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Article
| Open AccessCavity-free plasmonic nanolasing enabled by dispersionless stopped light
The stopped light principle engenders an inherent feedback mechanism for light. Pickering et al. study the implications of this local feedback in gain-enhanced plasmonic nanostructures and find the natural emergence of ultrafast photonic and plasmonic cavity-free lasing on the nanoscale.
- Tim Pickering
- , Joachim M. Hamm
- & Ortwin Hess
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Angular momentum-induced circular dichroism in non-chiral nanostructures
The differential absorption of left and right handed light, circular dichroism, is typically observed only in chiral objects. Here, the authors demonstrate that giant circular dichroism can be induced in non-chiral objects when the left and right handed circularly polarized modes used are vortex beams.
- Xavier Zambrana-Puyalto
- , Xavier Vidal
- & Gabriel Molina-Terriza
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Highly efficient inverted polymer light-emitting diodes using surface modifications of ZnO layer
Light trapped in the active polymeric layer limits the total efficiency of polymer light-emitting diodes. Here, Lee et al.get round this bottleneck by enhancing light extraction in waveguide optical modes via ripple-shaped nanostructures that spontaneously form on ZnO electrode surfaces.
- Bo Ram Lee
- , Eui Dae Jung
- & Myoung Hoon Song
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Photovoltaic effect in few-layer black phosphorus PN junctions defined by local electrostatic gating
Ambipolar transport, necessary to realise PN-junctions, is unfortunately missing from most two-dimensional semiconductors. Here, the authors fabricate few-layer black phosphorous field-effect transistors, define PN-junctions and demonstrate full electrostatic control of the device by means of local gating.
- Michele Buscema
- , Dirk J. Groenendijk
- & Andres Castellanos-Gomez
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X-ray holography with a customizable reference
X-ray Fourier-transform holography has been restricted by a limited choice of reference waves. Here, Martin et al.demonstrate X-ray Fourier-transform holography with an almost unrestricted choice for the reference wave, allowing greater flexibility in the design of holographic experiments.
- Andrew V. Martin
- , Adrian J. D’Alfonso
- & Henry N. Chapman
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An upconverted photonic nonvolatile memory
Conventional flash memory devices are voltage driven and found to be unsafe for confidential data storage. Here, the authors propose a light driven, rewritable photonic flash memory device based on upconversion nanocrystals with a high ON/OFF ratio and long retention time.
- Ye Zhou
- , Su-Ting Han
- & V.A.L. Roy
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Article
| Open AccessTemporal spying and concealing process in fibre-optic data transmission systems through polarization bypass
Recent temporal cloaking schemes hid or revealed temporal events and data using spectral modifications in a continuous wave probe. Here, Bony et al.propose using reversible manipulation of the polarization state of transmitted data to perpetually copy or conceal data in a fibre-optic transmission system.
- P.Y. Bony
- , M. Guasoni
- & J. Fatome
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Mechano-actuated ultrafast full-colour switching in layered photonic hydrogels
Photonic crystals used for many optical devices are the materials made of nanoscaled periodic structures that diffract light. Yue et al. design and fabricate a soft mechanochromic hydrogel that exhibits a fast colour switching rate at 0.1 ms in a full-colour band.
- Youfeng Yue
- , Takayuki Kurokawa
- & Jian Ping Gong
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Efficient optical extraction of hot-carrier energy
The thermalization of high-energy photons limits the efficient conversion of photon energy in photovoltaic applications. Here, Saeed et al. consider optical extraction of the excess energy of hot carriers by emission of infrared photons, using erbium ions in combination with silicon nanocrystals.
- S. Saeed
- , E. M. L. D. de Jong
- & T. Gregorkiewicz
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Multicolour nonlinearly bound chirped dissipative solitons
Stimulated Raman scattering limits the energy of dissipative solitons by converting excess energy into noisy Raman pulses. Using delay compensation, Babin et al. demonstrate that these noisy pulses can become coherent Raman dissipative solitons leading to the formation of multicolour bound dissipative soliton complexes.
- Sergey A. Babin
- , Evgeniy V. Podivilov
- & Alexander Apolonski
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Interface between path and orbital angular momentum entanglement for high-dimensional photonic quantum information
The orbital angular momentum of light is a promising degree of freedom for long-distance information transportation. To create high-dimensional entanglement for pairs of photons, Fickler et al.use an optical mode sorter in reverse to transfer entanglement between the path into the orbital angular momentum.
- Robert Fickler
- , Radek Lapkiewicz
- & Anton Zeilinger
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Light focusing in the Anderson regime
Anderson localization is a regime where diffusion is inhibited, leading to the localization of waves. Here, Leonetti et al.use wavefront shaping to achieve focusing in disordered optical fibres in the Anderson regime and demonstrate efficient focusing action.
- Marco Leonetti
- , Salman Karbasi
- & Claudio Conti
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Photocarrier relaxation pathway in two-dimensional semiconducting transition metal dichalcogenides
Two-dimensional semiconducting transition metal dichalcogenides strongly absorb visible light. Kozawa et al.study the photocarrier relaxation in mono- and bilayer MX2 samples and find that loss of photocarriers by direct recombination becomes a second-order process when excitation is in resonance with band nesting.
- Daichi Kozawa
- , Rajeev Kumar
- & Goki Eda
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Short-lived charge-transfer excitons in organic photovoltaic cells studied by high-field magneto-photocurrent
Organic magneto-transport is of interest due to numerous potential applications, including solar cells. Here, the authors study high-field magneto-photocurrent to analyse charge-transfer excitons in organic photovoltaic cells, showing that spin-mixing mechanisms are operational over 8 Teslas.
- Ayeleth H. Devir-Wolfman
- , Bagrat Khachatryan
- & Eitan Ehrenfreund
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Solar steam generation by heat localization
Steam generation from solar energy is currently inefficient because of costly high optical concentration and large heat losses involved. Ghasemi et al. develop an efficient approach with internal efficiency up to 85% at low water temperature using a carbon-based material with a double-layer structure.
- Hadi Ghasemi
- , George Ni
- & Gang Chen
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Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics
The applications of graphene and transition metal dichalcogenides in electronics are limited by their zero-bandgap and low mobility, respectively. Here, the authors demonstrate the potential of an emerging layered material—black phosphorous—for thin film electronics and infrared optoelectronics.
- Fengnian Xia
- , Han Wang
- & Yichen Jia
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| Open AccessHigh-mobility transport anisotropy and linear dichroism in few-layer black phosphorus
Two-dimensional (2D) materials with a large electronic bandgap in addition to high carrier mobility are required for future nanoelectronics. Here, the authors present a theoretical investigation of black phosphorous, a new category of 2D semiconductor with high potential for nanoelectronic applications.
- Jingsi Qiao
- , Xianghua Kong
- & Wei Ji
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Article
| Open AccessBright emission from a random Raman laser
Unlike conventional lasers that require a uniform resonant cavity to operate, random lasers use a highly disordered gain medium in which scattering is dominant. Hokr et al. report Raman lasing from a bulk three-dimensional disordered medium whose intensity exceeds that of other random lasers by many orders of magnitude.
- Brett H. Hokr
- , Joel N. Bixler
- & Vladislav V. Yakovlev
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Article
| Open AccessLasing from active optomechanical resonators
Vertical-cavity surface-emitting lasers consist of an active medium in between two distributed Bragg reflectors. Czerniuk et al.show that the resonant mechanical modes of these periodic structures efficiently modulate the laser emission intensity with frequencies of up to 40 GHz.
- T. Czerniuk
- , C. Brüggemann
- & M. Bayer
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Nanophotonic integrated circuits from nanoresonators grown on silicon
The integration of photonic components on silicon chips creates the challenge of achieving a uniform and efficient architecture. Here, the authors demonstrate on-chip light-emitters, photodetectors, photovoltaic power supply and optical data link, all based on InGaAs nanoresonators grown on silicon.
- Roger Chen
- , Kar Wei Ng
- & Connie Chang-Hasnain
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| Open AccessImaging and steering an optical wireless nanoantenna link
Like conventional antennas, optical nanoantennas can transmit and receive signals but on much smaller length scales. Dregely et al.measure the optical power transmitted and received in the far-field by plasmonic nanoantennas and show that they can control the direction of transmission over a broad range.
- Daniel Dregely
- , Klas Lindfors
- & Harald Giessen
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Approaching the limits of transparency and conductivity in graphitic materials through lithium intercalation
Graphene-based materials have potential as transparent electrodes, but still fall short of desired performance goals. Here, Bao et al.report that upon intercalation of lithium into few-layer graphene, desired sheet resistance and optical transmittance may be achieved.
- Wenzhong Bao
- , Jiayu Wan
- & Liangbing Hu
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Article
| Open AccessRotated waveplates in integrated waveguide optics
Integrated photonic circuits with arbitrary control over the light polarization state are important in quantum information applications. Corrielli et al. realize compact quantum state tomography of polarization-entangled photons using waveguide-integrated waveplates fabricated by femtosecond laser inscription.
- Giacomo Corrielli
- , Andrea Crespi
- & Roberto Osellame
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| Open AccessEnhanced carrier multiplication in engineered quasi-type-II quantum dots
Carrier multiplication can improve the performance of solar cells, but its efficiency is still not high enough to considerably increase the power output of practical devices. Cirloganu et al.show that appropriately designed core-shell quantum dots can enhance the carrier multiplication yield four-fold.
- Claudiu M. Cirloganu
- , Lazaro A. Padilha
- & Victor I. Klimov
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| Open AccessAn ultralow power athermal silicon modulator
Optical modulators on silicon promise to deliver ultralow power communication networks between or within computer chips. Here, the authors demonstrate a silicon modulator operating with less than one femtojoule energy and are able to compensate for thermal drift over a 7.5 °C temperature range.
- Erman Timurdogan
- , Cheryl M. Sorace-Agaskar
- & Michael R. Watts
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| Open AccessMonolithically integrated mid-infrared lab-on-a-chip using plasmonics and quantum cascade structures
Quantum cascade lasers and detectors enable photonic integration of semiconductor devices across a broad spectral range. Here, Schwarz et al.present a bi-functional laser and detector structure, monolithically integrated with plasmonic waveguides for mid-infrared chemical sensors on a chip.
- Benedikt Schwarz
- , Peter Reininger
- & Gottfried Strasser
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Waveforms for optimal sub-keV high-order harmonics with synthesized two- or three-colour laser fields
The promise of X-ray tabletop broadband light sources by high-order harmonics generated in a gas medium has been limited by low conversion efficiencies. Here, Jin et al.show a method to enhance the high harmonic generation by optimizing the waveform of synthesized two and three colour laser fields.
- Cheng Jin
- , Guoli Wang
- & C. D. Lin
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High-efficiency organic light-emitting diodes with fluorescent emitters
Fluorescent organic light-emitting diodes hold promise for next-generation full-colour displays, but are currently limited by the internal electroluminescence quantum efficiency. Nakanotani et al.break this limit and demonstrate nearly 100% efficiency in a double-dopant system without a rare metal.
- Hajime Nakanotani
- , Takahiro Higuchi
- & Chihaya Adachi
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Spectrally selective chiral silicon metasurfaces based on infrared Fano resonances
Despite their two-dimensional nature, metasurfaces offer flexible and efficient control over the properties of light passing through them. Here, the authors realize chiral silicon-based metasurfaces for applications as polarizers or as emitters of polarized thermal radiation.
- Chihhui Wu
- , Nihal Arju
- & Gennady Shvets
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Article
| Open AccessRegeneration limit of classical Shannon capacity
The Shannon limit describes the limit of error-free information transmission and thus the information that can be transmitted in telecommunications. Here, the authors derive the Shannon limit for nonlinear, regenerative systems, expanding on the classical linear case.
- M. A. Sorokina
- & S. K. Turitsyn
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Non-invasive classification of microcalcifications with phase-contrast X-ray mammography
X-ray absorption imaging is used for early breast cancer detection but can barely identify the morphology of microcalcifications—a possible indicator of cancer. Wang et al.develop a technique to non-invasively classify different types of microcalcifications and achieve 100% sensitivity on phantom data.
- Zhentian Wang
- , Nik Hauser
- & Marco Stampanoni
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| Open AccessMagnetophoretic circuits for digital control of single particles and cells
One of the main goals of lap-on-a-chip systems is to manipulate single particles with automation of modern-day computer circuits. Lim et al.develop an integrated circuit for transporting magnetic particles with time-varying magnetic fields that can be applied to the parallel analysis of single cells.
- Byeonghwa Lim
- , Venu Reddy
- & CheolGi Kim
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Macromolecular structures probed by combining single-shot free-electron laser diffraction with synchrotron coherent X-ray imaging
Macromolecular complexes hold promise for future generations of drug delivery carriers, but probing their structures with high resolution is challenging. Here, the authors combine X-ray free-electron laser and synchrotron approaches to reveal the core-shell structure of RNA interference microsponges.
- Marcus Gallagher-Jones
- , Yoshitaka Bessho
- & Changyong Song
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Few-femtosecond time-resolved measurements of X-ray free-electron lasers
Characterizing femtosecond X-ray pulses that vary from shot to shot is important for data interpretation. Here, Behrens et al.measure time-resolved lasing effects on the electron beam and extract the temporal profile of X-ray pulses using an X-band radiofrequency transverse deflector.
- C. Behrens
- , F.-J. Decker
- & J. Wu
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Generation of 1020 W cm−2 hard X-ray laser pulses with two-stage reflective focusing system
X-ray-free electron lasers produce X-ray pulses for use in applications such as the determination of molecular structures or the study of materials. Here, Mimura and colleagues demonstrate a two-stage focusing scheme to achieve unprecedented laser power densities of over 1020 W cm−2.
- Hidekazu Mimura
- , Hirokatsu Yumoto
- & Kazuto Yamauchi
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Article
| Open AccessSpectral interferometric microscopy reveals absorption by individual optical nanoantennas from extinction phase
Absorption by an optical nanoantenna determines its interaction strength with light, yet this quantity is hidden from conventional spectroscopy. Gennaro et al. now demonstrate a spectroscopic technique that reveals a nanoantenna’s absorption by recovering its amplitude and phase response.
- Sylvain D. Gennaro
- , Yannick Sonnefraud
- & Rupert F. Oulton
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Experimental plug and play quantum coin flipping
A quantum implementation of coin flipping—a cryptographic primitive allowing distrustful parties to agree on a random bit—may offer security advantages over classical implementations. Pappa et al.enhance a commercial quantum key distribution system to prove such advantages over long distances.
- Anna Pappa
- , Paul Jouguet
- & Eleni Diamanti
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Supersymmetric mode converters
In its optical manifestation, supersymmetry can potentially establish close relationships between seemingly different dielectric structures. Here, the authors use the perfect global phase matching afforded by supersymmetry for mode conversion and mode division multiplexing in highly multimoded systems.
- Matthias Heinrich
- , Mohammad-Ali Miri
- & Demetrios N. Christodoulides
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Optofluidic sorting of material chirality by chiral light
Sorting of material chirality is demanded in many industries, and conventional strategies are limited to the usage of chiral shape of the entity to be sorted. Tkachenko and Brasselet present a passive optical sorting method to achieve the same goal, which relies on the chirality–light interaction.
- Georgiy Tkachenko
- & Etienne Brasselet
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Excitons versus free charges in organo-lead tri-halide perovskites
The performance of perovskite-based solar cells has improved dramatically in recent years, yet surprisingly little is known about the details of how they work. Grancini et al. report results that suggest that their behaviour is dominated by the transport of free carriers rather than excitons.
- Valerio D’Innocenzo
- , Giulia Grancini
- & Annamaria Petrozza
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Smart responsive phosphorescent materials for data recording and security protection
Smart luminescent materials have many potential applications. Here, the authors synthesize a series of responsive iridium complexes, with tunable emission colours, and use their mechano-, vapo- and electrochromic phosphorescence properties to construct a proof of concept data recording device.
- Huibin Sun
- , Shujuan Liu
- & Wei Huang
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Article
| Open AccessSynthetic optical holography for rapid nanoimaging
Holography provides amplitude and phase information when imaging objects, which enables greater understanding of a range of samples. Here, the authors adapt holography to scanning near-field optical microscopy, providing rapid phase-resolved imaging on the nanoscale at visible and infrared frequencies.
- M. Schnell
- , P. S. Carney
- & R. Hillenbrand
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An experimental implementation of oblivious transfer in the noisy storage model
The oblivious transfer protocol is a cryptographic primitive used to create many different secure two-party schemes. Here, Erven et al. provide the first implementation of the oblivious transfer protocol using entangled photons, within the noisy storage model.
- C. Erven
- , N. Ng
- & G. Weihs
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Elucidating the charge carrier separation and working mechanism of CH3NH3PbI3−xClx perovskite solar cells
Rapid progress has been made in the development of perovskite-based solar cells, but how they work has been unclear. Electron beam-induced current measurements performed in a scanning electron microscope by Edri et al.show they operate as a p–i–n solar cell with a high electronic quality absorber.
- Eran Edri
- , Saar Kirmayer
- & David Cahen
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Article
| Open AccessOptical properties of relativistic plasma mirrors
Next generation high power lasers will produce fields so intense they can only be controlled with components made of plasmas. Vincenti et al.explore the properties of one such component—the relativistic plasma mirror—and construct an analytical framework to improve their use in focusing intense laser fields.
- H. Vincenti
- , S. Monchocé
- & F. Quéré
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